There are presently many concerns with the possible adverse health conditions associated with elevated nitrate content of water. Nitrate con enter the water supply from natural sources but also can come from fertilizer use, and the like. The concerns surrounding elevated nitrate levels become with potable water, but are also present with waste waters and the like.
A body of references exist which are directed to methods for the removal of nitrate from water or to the measurement of nitrate in water. U.S. Pat. No. 4,671,879 to Solt et al. describes a method for reducing the nitrate content in water using an ion-exchange resin. U.S. Pat. No. 4,622,133 to Furano describes a dual train system for removing ions such as nitrate from water. U.S. Pat. No. 3,775,088 to Higgins describes another nitrate removal system.
Examples of apparatus for analyzing liquids for their ion content include the system shown in U.S. Pat. No. 3,785,771 to Luchsinger et al. This patent describes a method for removing macromolecules so that they will not interfere with later ion measurements. U.S. Pat. No. 4,681,025 to Dalgaard, describes a system for monitoring pH (hydrogen ion content) in the presence of other potentially interfering ions. This patent shows using cation exchange resins to remove ions which interfere with pH measurement. Another representative reference is U.S. Pat. No. 4,251,219 to Larson et al., which describes a system for measuring low levels of chloride, sulfate, phosphate, nitrate and other ions in a low-pressure condensate. U.S. Pat. No. 4,314,823 to Rich et al., describes a combination conductivity and ion-exchange resin system which allows qualitation and quantitation of a mixture of chlorides, carbonates, acetates, formates, and the like.
The present invention id directed specifically to an analyzer system designed to permit the measurement of nitrate ions in the presence of other contaminating species, particularly chloride and bicarbonate.